AlphaOmegaKid writes:
Let's try to nail down your major claims:
Claim: Large mammals are subject to reduced natural selection.
Cited evidence: Endangered species
Rebuttal: Endangered species are the result of human interference, and the reduced natural selection is a result of additional human interference applied as a remedy for the original human interference. Before, say, a million years ago, what caused large mammals to be subject to reduced natural selection?
C'mon Percy, this is a complete strawman. You cannot cite anywhere that I have claimed anything close to this.
You said this in several places, originally in your
Message 109:
In organisms with large genomes, low fecundity, and long generation times (most large mammals), they cannot afford the cost of selction without severe inbreeding depression. So the population continues to exist under reduced selective pressures and the mutations just add up over time. The adding up problem is what "genetic entropy" is.
So apparently you did say it. And now in today's message you say much the same thing:
3. If these large mammals have increased selection to remove the mutations, then the population size becomes smaller, and yes, there are plenty of species in this category. They are endangered.
But this time you refer just to
selection instead of
selection pressures. You evidently think that increasing accumulations of slightly deleterious mutations will cause increasing numbers of individuals to be removed from the population through natural selection, threatening the population with extinction. And you apparently also think that selection must therefore be reduced in order for these populations to survive.
And as been explained to you many times now, endangered species are predominantly the result of human interference, as is any reduction in selection pressures. So before man came on the scene, what was the cause of this reduction in selection?
1. They have high mutation rates which clearly are vastly more deleterious than advantageous. Most mammals have this.
The mutation rate in large mammals is about the same as all other mammals.
This claim is closer, but not exact. It doesn't matter is the mutations are fixed or not. It just matters that their frequency is increasing over time.
Mutations occur at a more or less constant rate. What you're trying to say is that the unfavorable mutations are not removed from the population and so accumulate over time. You're trying to say that increasing numbers of deleterious mutations become prevalent in the population.
The first and primary evidence of this is Mendel's Accountant.
A modelling program is now evidence? I don't think so, and in any case it is overwhelmed in numbers by the many evolutionary modelling programs out there that correctly demonstrate the principles of evolution.
Secondly, I think endangered species is also clear evidence of this.
Endangered species are predominantly caused by humans through loss of habitat or overfishing or overhunting or climate change, etc. They are not caused by the spread of deleterious mutations causing a reduction in fitness.
Thirdly, the most genetically studied species (humans) offers clear evidence of this.
What humans are doing is adapting to our existing environment, which in the developed world consists of expert medical care, abundant food, protection from the weather, and safety from predators.
Haldane was the first to realize this when he discovered that there is a cost of natural selection. That cost limits the powers of natural selection. Natural selection is not powerful enough to remove all the negative mutations and leave the good ones.
You are incorrect. This is from the Wikipedia article on Haldane:
Wikipedia writes:
Haldane stated at the time of publication "I am quite aware that my conclusions will probably need drastic revision", and subsequent corrected calculations found that the cost disappears.
Moving on:
We have big problems if our mutation rate is anything like as high as 0.5. Wow, wait till he finds our our real mutation rate!
Mueller's u
t is not a mutation rate but a derived figure that I'm guessing is the probability of a deleterious mutation occurring during a reproductive event, but he bases u
t on an assumed value of 5x10
-5 for the probability of a point mutation for any single nucleotide (see page 126), and we know that it is actually in the 10
-8 neighborhood, so he's off by three orders of magnitude.
You are correct that if deleterious mutations occur faster than natural selection can remove them then extinction is a likely outcome. And you can plug such numbers into programs like Mendel's Accountant or any other evolution modelling program and they will verify this is true. But the reality is that mutation rates are tiny, and fixation of mutations that reduce fitness is very unlikely.
Neel also realized this. His calculation of our muation rate was 30! This is what he said about it...
I think you're confusing different types of numbers. In some of what you're reading they're providing the number of mutations per individual. In other places they may be providing the number of new mutations in the population per generation. In yet other places they're talking about the probability of a mutation in a base pair, a point mutation, during a reproductive event. So when Neel said this:
Neel writes:
If this approximation is correct, then gamete rates for "point" mutations become of the order of 30 per generation.
You can't compare Neel's "30 per generation" to Mueller's u
t. Mueller's number is a probability, Neel's is a rate. And Neel's number is based on a more accurate value for the probability of a point mutation of 10
-8 than Mueller's 10
-5.
By the way, Neel also said this:
Neel writes:
The error of this estimate is large and somewhat indeterminate, but at this stage in our study of mutation rates at the molecular level we are still confronted with fixing orders of magnitude.
Given that he was writing 25 years ago, you might want to delve into some more recent research. One recent estimate I heard for human mutations was 100 per reproductive event.
About Kondrashov, you actually quoted him conceding that his model doesn't reflect reality, and that he was seeking possible improvements. And the same with Nachman and Crowell. You actually quoted them conceding that their model couldn't possibly reflect reality since it would require 40 offspring to produce 2 viable offspring, which obviously never happens. They, too, are seeking improvements and refinements to their model.
Let's sum up. You think that the large number of endangered species is due to the inevitable decline in fitness of populations due to accumulating deleterious mutations, and that it doesn't have anything to do with human interference in habitat and so forth. There's no evidence to support this view of endangered species, nor that accumulating mutations doom populations.
In 1859, coincidentally the same year
Origin of Species was published, 24 rabbits were introduced into Australia. Their population quickly exploded, and within 30 years rabbits became a serious problem. This happened because they proved well adapted to the Australian environment. Had the rabbits been instead introduced into Antarctica their numbers would have quickly dropped to zero, and accumulating deleterious mutations would have nothing do with it. Just as they have nothing to do with creating endangered species.
--Percy
Edited by Percy, : Major clarification, meaning is unchanged.
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